Method for determining desired components of quadrature modulated signals

Abstract

In the following manner, a receiver that receives quadrature modulated signals may determine desired components of the quadrature modulated signals by minimizing effects of transmitted distortion produced by gain, phase, or gain-phase imbalance. A quadrature modulated signal that includes a desired component, a fading component, and a transmitter distortion component is received by the receiver, wherein the transmitter distortion component includes a conjugate component and an imbalance component. The receiver estimates the fading component, the conjugate component, and the imbalance component and determines the desired component based on these estimates and the quadrature modulated signal.

We claim: 
     
       1. In a receiver that receives quadrature modulated signals, a method for determining desired components of the quadrature modulated signals by minimizing effects of transmitted distortion produced by gain, phase, or gain-phase imbalance in a transmitter that transmitted the quadrature modulated signals, the method comprises the steps of: a) receiving a quadrature modulated signal, wherein the quadrature modulated signal includes a desired component, a fading component, and a transmitter distortion component and wherein the transmitter distortion component includes a conjugate component and an imbalance component;   b) estimating, by the receiver, the fading component to produce an estimated fading component;   c) estimating, by the receiver, the conjugate component to produce an estimated conjugate component;   d) estimating, by the receiver, the imbalance component to produce an estimated imbalance component;   e) determining, by the receiver, the desired component based on the quadrature modulated signal, the estimated fading component, the estimated conjugate component, and the estimated imbalance component.   
     
     
       2. In the method of claim 1, step (d) further comprises the steps of: d1) selecting an initial value of the imbalance component;   d2) estimating a first estimated desired component estimate; and   d3) estimating the imbalance component based on the quadrature modulated signal, the first estimated desired component, the initial value of the imbalance component, the estimated conjugate component, and the estimated fading component.   
     
     
       3. In the method of claim 1, step (e) further comprises the steps of: e1) multiplying the estimated fading component by a product of the estimated conjugate component and the estimated imbalance component to produce an undesired component;   e2) subtracting the undesired component from the quadrature modulated signal to produce a compensated quadrature signal; and   e3) determining the desired component based on a ratio of the compensated quadrature signal to the estimated fading component.   
     
     
       4. In the method of claim 1, wherein the quadrature modulated signal includes a pre-established parameter portion, step (b) further comprises estimating the fading component based on predetermined knowledge of the pre-established parameter portion. 
     
     
       5. In the method of claim 2, step (d3) further comprises the steps of: d3a) utilizing closed loop feedback to determine an error signal based on the quadrature modulated signal, the first estimated desired component, the initial value of the imbalance component, the estimated conjugate component, and the estimated fading component;   d3b) estimating the imbalance component based on the initial value of the imbalance component and the error signal to produce an imbalance component estimate;   d3c) continuing to update the imbalance component estimate, via the closed loop feedback, until the error signal is negligible.   
     
     
       6. In the method of claim 2, step (d3) further comprises estimating the imbalance component based on accumulations of the quadrature modulated signal, the first estimated desired component, the estimated conjugate component, and the estimated fading component over a predetermined period of time. 
     
     
       7. In a receiver that receives quadrature modulated signals, wherein the quadrature modulated signals include at least two subchannel signals, a method for determining desired components of the quadrature modulated signals by minimizing effects of transmitted distortion produced by gain, phase, or gain-phase imbalance in a transmitter that transmitted the quadrature modulated signals, the method comprises the steps of: a) receiving a quadrature modulated signal, wherein each subchannel signal of the at least two subchannel signals includes a desired component, a fading component, and a transmitter distortion component and wherein the transmitter distortion component includes a conjugate component and an imbalance component;   b) estimating, by the receiver, the fading component of the each subchannel signal to produce estimated fading components;   c) estimating, by the receiver, the conjugate component of the each subchannel signal based on the desired component of a corresponding mirror image subchannel signal of the at least two subchannel signals to produce estimated conjugate components;   d) estimating, by the receiver, the imbalance component to produce an estimated imbalance component;   e) determining, by the receiver, the desired component of the each subchannel signal based on the quadrature modulated signal, the estimated fading components, the estimated conjugate components, and the estimated imbalance component.   
     
     
       8. In the method of claim 7, step (d) further comprises the steps of: d1) selecting an initial value of the imbalance component;   d2) estimating the desired component of the each subchannel signal to produce a first estimate of each desired component; and   d3) estimating the imbalance component based on the quadrature modulated signal, the first estimate of each desired component, the initial value of the imbalance component, the estimated conjugate components, and the estimated fading components.   
     
     
       9. In the method of claim 7, step (e) further comprises the steps of: e1) multiplying each of the estimated fading components by a corresponding one of the estimated conjugate components and the estimated imbalance component to produce undesired components;   e2) subtracting each of the undesired components from the quadrature modulated signal to produce compensated quadrature signals; and   e3) determining the desired component of the each subchannel signal based on a ratio of each of the compensated quadrature signals to a corresponding one of the estimated fading components.   
     
     
       10. In the method of claim 7, wherein each of the at least two subchannel signals includes a pre-established parameter portion, step (b) further comprises estimating the fading component of the each subchannel signal based on predetermined knowledge of the pre-established parameter portion. 
     
     
       11. In the method of claim 8, step (d3) further comprises the steps of: d3a) utilizing closed loop feedback to determine an error signal based on the quadrature modulated signal, the first estimate of each desired component, the initial value of the imbalance component, the estimated conjugate components, and the estimated fading components;   d3b) estimating the imbalance component based on the initial value of the imbalance component and the error signal to produce an imbalance component estimate;   d3c) continuing to update the imbalance component estimate, via the closed loop feedback, until the error signal is negligible.   
     
     
       12. In the method of claim 8, step (d3) further comprises estimating the imbalance component based on accumulations of the quadrature modulated signal, the first estimate of each desired component, the estimated conjugate components, and the estimated fading components over a predetermined period of time.